"That, too, may always remain a mystery," continued the other, reflectively, "but an arrangement could have been made whereby certain stones that were laid down in a peculiar manner would direct him to search in a hollow stump or under a log for a letter. All we know is that this traitor did receive his message, and started to tear it to pieces, but on second thought kept part of the letter." "It will be his undoing yet, sir, I think," Roger ventured to suggest. "Too bad there was no name mentioned, so we could charge him with the deed, and punish him as he deserves. I am wild to know who he is, for I shall long remember how he tried to put an end to us in the rapids of the Yellowstone." "Perhaps you may, and that before another dawn comes," remarked the captain, as he smiled indulgently at the headstrong boy, whom he had come to like very much, as, indeed, he did Dick, also. "That sounds as though you had made a plan of campaign, Captain," Dick observed, with a pleased look that was only exceeded by the smile on the face of his companion. "I have laid out a little scheme which I think may work well, and trap the guilty wretch in the toils," explained the captain. "You remember the special mention made of guns and ammunition, which he was told to take with him, if he really believed his usefulness in the camp had come to an end? That gave me my clew." "The bait will be a stock of powder and ball, and perhaps several guns, unless I fail to catch your meaning, sir?" Dick continued. "Before we go to sleep, to-night, I shall have three men, whose names I need not mention, know that there are several good guns, and quite a quantity of ammunition for them, in the supply tent where we keep our extra provisions. It is not guarded beyond the fact that sentries are posted outside the camp to watch for enemies. But to-night both of you boys, together with myself and Captain Clark, will be in hiding, ready to capture any one who ventures to enter that supply tent." "Thank you for thinking of us, sir," exclaimed Roger, warmly. "Why should I not do so, when the first intimation I received that there was a traitor in the camp came through you two boys? And, besides, you are more deeply interested in his capture and punishment than any of the others, because this unknown spy is working hand and glove with François Lascelles, who hates you most bitterly." "Tell us what to do, Captain, and you can rely on our working with you to the best of our ability," Dick assured the commander, who smiled at him and went on to explain further.